Field of the Invention
The present invention relates to a seat supporting structure equipped on a working vehicle.
Related Art
As disclosed by JP H05-229377 A, a well-known conventional tractor referred to as a tractor-loader-backhoe is equipped at a front portion thereof with a front loader, and at a rear portion thereof with a backhoe. This tractor is forward-turned for traveling and for loading and is backward-turned for excavation by the backhoe. Therefore, the tractor includes a seat support structure that pivotally supports an operator's seat on a vertical axis so as to enable the seat to face forward and backward. Further, the tractor has a front footboard for an operator sitting on the forward-facing seat and a rear footboard for an operator sitting on the backward-facing seat, and the front and rear footboards have different heights. Therefore, when the seat is turned to change its forward or backward facing direction, the height of the seat has to be changed. Therefore, the seat support structure includes a parallel link mechanism for translating the seat upward and downward so as to change the height of the seat.
The seat support structure also includes an upper support plate and a lower fixed plate. The seat is rotatably supported on the supporting plate, and the parallel link mechanism is interposed between the supporting plate and the fixed plate. In this regard, the parallel link mechanism includes four parallel links, i.e., right and left front links and right and left rear links. The four parallel links are pivoted at lower ends thereof onto the fixed plate and are pivoted at upper ends thereof onto the supporting plate, so that rotation of the four parallel links changes the height of the supporting plate and the seat relative to the fixed plate.
The seat support structure needs a large space between the supporting plate and the fixed plate and among the four parallel links because this space has to accommodate a height-control means for rotating the parallel links to change the height of the supporting plate relative to the fixed plate, a seat-location means for locating the rotational position of the seat relative to the supporting plate, and a rotation locking means for locking the rotation of the seat relative to the supporting plate. As a result, it is difficult to minimize the seat support structure.